Casemiro has made 159 appearances and scored 26 goals for Manchester United.

"One more year, one more year, Casemiro." They know it won't happen, but it won't stop Manchester United's fans belting out their ode to the Brazilian when he makes his final Old Trafford appearance for the club against Nottingham Forest on Sunday.

It has been sung frequently at United games over the second half of the season, especially when Casemiro has scored, and most recently when he gave his side an early lead in a key Premier League game against Brentford last month. The 34-year-old responded by kissing and pointing to the badge on his shirt. United's supporters lapped it up.

It was all a far cry from 30 December 2024. That was a day of infamy among the normally loyal and vociferous United fanbase as they turned on striker Joshua Zirkzee, when he was substituted in just the 33rd minute by Ruben Amorim during a particularly woeful home defeat by Newcastle. The unspoken reality of that day was that, while the reaction to Zirkzee's exit was bad, had Casemiro's number been held up, it would have been even worse, such was the veteran's ineffective contribution to a dreadful team performance. As it turned out, the midfielder was replaced after 64 minutes. He didn't play again for a month and didn't start for nearly seven weeks.

As Amorim reflected at the time: "Even Toby Collyer was sometimes playing in front of him." That was nine months after Jamie Carragher's damning "leave the football before the football leaves you" comment following a 4-0 defeat at Crystal Palace in May 2024 that led Erik ten Hag to the brink of dismissal as manager, before the FA Cup final success later that month in which Casemiro was left out completely.

In January 2025, there were few external criticisms of Carragher's assessment, which Casemiro branded "disrespectful" in an interview on Rio Ferdinand's podcast, which was published earlier this week. Amorim felt Casemiro - a five-time Champions League winner with Real Madrid - did not have the physical capabilities to be effective in the Premier League.

It took three months of hard work to change Amorim's mind. On 6 March 2025, he started the first leg of the Europa League last-16 draw with Real Sociedad. He kept his place for the league game against Arsenal and, from that point, has started every major game United have played.

"Football changes. Life changes," Casemiro said in his recent interview with former United captain Ferdinand. "For me, [with] the best players in the world, it's about the mentality. I might not play good - I'm not a robot and I know. But the next [game], I give everything on the pitch. The mentality is next, next, next."

It is a mentality that has brought Casemiro back into the Brazil squad - he is expected to be Carlo Ancelotti's captain at this summer's tournament. This season, the 34-year-old's influence has noticeably increased. Of all the players in Michael Carrick's squad, it is widely accepted if Casemiro had been injured in February, after the transfer deadline had closed, his absence would have been the hardest to cover in the ultimately successful quest for Champions League qualification.

"He has been an absolute pleasure to work with," Carrick says in his programme notes for the Forest game. "He will always have a special connection with Manchester United."

Carrick has felt the early clarity around Casemiro's exit - announced on 22 January, days after the manager's own return as Amorim's temporary replacement - has been beneficial for player and club. Aside from the mentality aspect, the player's influence at Old Trafford should extend far longer than his physical presence.

When Casemiro arrived from Real Madrid in 2022 in a deal worth up to £70m, Kobbie Mainoo, then aged 17, felt he would learn huge amounts from one of the most decorated players in the game. Amid the Brazilian's collapse in form, Mainoo ended up battling for a start with Casemiro, which wasn't a situation he envisaged. The clear by-product of Amorim's exit has been the partnership between the pair, who have played alongside each other in 13 of Carrick's 15 matches in charge - a one-match absence for both players because of minor injuries the only reason it was not 15 out of 15.

"Kobbie is my friend," Casemiro explained earlier this month in a separate interview with the respected United We Stand fanzine. "I have an excellent relationship with him. We are always joking - in English because he doesn't speak Portuguese. "He is a complete player, the present and the future of Manchester. Why? Because he has already taught us that he can play to a high level for his club and country. The one thing he needs to improve is to play more with the ball, to touch the ball more, because he has so much quality. Then it's the decision-making which comes with experience. That improves with age."

Manchester United midfielder Casemiro kisses the badge on his shirt after scoring against Brentford.

Helping Mainoo fulfil his potential and utilise the talent if felt as if everyone could see, except Amorim, would be a fitting postscript for Casemiro, who will always return to Old Trafford a hero no matter what the future holds. A move to Major League Soccer has been predicted after the World Cup is done. The immediate focus, though, is Forest and his Old Trafford farewell, with those "one more year" chants echoing around the stadium once more.

"It's incredible, just incredible," Casemiro told United We Stand. "My son (five-year-old Caio) is a Manchester United fan. He knows the songs and sings them at home. When the team loses, he cries.

"Our box is right on top of where the noisy United fans are. They feel this spirit. The most important thing about this club are the fans. Many times, we lose a game but in the next game they support us more. For me, that's incredible. I've never experienced that in my career."